What is a Pulse Oximeter? and Quick Tips on getting the right one

June 28, 2022 - Parul Saini, Webmedy Team

Updated Version - July 25, 2023

With health and safety becoming a top priority, especially with COVID-19 being so prevalent, people are looking for ways to manage their health at home. Medical devices such as pulse oximeters have become essential for personal health monitoring.


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This article provides you with a comprehensive guide to everything about pulse oximeters, from what a normal reading looks like, to tips and advice for choosing the best one for you.

Discover what pulse oximeters are capable of, as well as how they work...

What is a Pulse Oximeter?

A pulse oximeter is a small, clip-like medical device. It attaches to a body part, most commonly to a finger. A pulse oximeter uses a non-invasive method for monitoring a person's blood oxygen saturation (as opposed to measuring oxygen saturation directly through a blood sample). It can rapidly detect even small changes in oxygen levels.

How does a Pulse Oximeter Work?

Pulse oximeters use a noninvasive method for monitoring a person's oxygen saturation, which is a measure of the percentage of oxyhemoglobin (oxygen-bound hemoglobin) in the blood.

Pulse oximeter utilizes the principle that oxyhemoglobin (oxygen-bound hemoglobin) and deoxygenated hemoglobin (that does not have oxygen bound to it) have different absorptions for different wavelengths of light.

A sensor device is placed on a thin part of the patient's body, usually a fingertip, earlobe, or an infant's foot. The device emits light in two wavelengths through the body part to a photodetector on the other side, which detects and measures the changing absorbance at each of the wavelengths. Oxyhemoglobin and deoxygenated hemoglobin absorb light of the two wavelengths in different ways. Thus, the device detects the amount of oxyhemoglobin and deoxygenated hemoglobin in arterial blood and shows it as Oxyhemoglobin saturation (SpO2), which is an indirect estimation of arterial oxygen saturation (SaO2).

What is a good Pulse Oximeter Reading?

Your pulse oximeter will show you your oxygen level as "SpO2." Normal oxygen levels are at least 95%. Some patients with chronic lung disease or sleep apnea can have normal levels of around 90%.

If your SpO2 level is less than 95%, you need to visit a doctor, as it may be an indication that you may be suffering from hypoxia, a condition that requires observation and treatment.

What are the two readings on a Pulse Oximeter?

  • Blood Oxygen Saturation (SpO2): The measurement that indicates what percentage of blood is saturated.
  • Pulse Rate: Pulse rate is nothing but the heart rate that indicates the number of times a heart beats per minute.

Different types of Pulse Oximeters

  • Fingertip Pulse Oximeters

    This type is most commonly used at home. It is small, rectangular-shaped, and clipped on the finger. The display screen is on the probe itself. This type is usually battery-operated. It is commonly used to spot-check oxygen saturation by clinicians, caregivers, or patients themselves.

  • Handheld Pulse Oximeters

    This is mostly used by medical institutes and hospitals since it is slightly more sophisticated and gives more accurate readings. The probe is attached to a cable connected to the screen. To get a reading, the probe must be attached to the person's finger - ideally the index finger. This type of oximeter is utilized for spot checks but is also capable of continuous oxygen saturation monitoring. It is usually utilized by hospitals, ambulatory health settings, homes, or EMS.

  • Tabletops with Sensors

    This model is usually bigger than a handheld pulse oximeter. It is capable of spot checks and continuous monitoring. Its size makes it ideal for hospitals, medical facilities, home care, and subacute settings.

  • Wrist-worn Sensors

    This model is wireless and usually used for continuous monitoring. Your doctor may want to monitor your oxygen levels daily or while you sleep, making this model ideal. This instrument is designed like a wristwatch. A small wire connects the probe, placed on the index finger, to a small monitor on the wrist. The readings will appear on this wrist monitor.

  • Pediatric Pulse Oximeters

    Children's pulse oximeters are designed to fit snugly on small fingers. Some varieties can attach to the foot or head that may work better if the child's fingers are very small.

Tips on what to look for in a Pulse Oximeter

  • Accuracy

    The accuracy of the results is very important irrespective of the fact whether you are buying it for the clinic or your personal needs.

  • Alarms

    Certain pulse oximeters would give out audible sounds to alert users of low oxygen saturation. This is helpful for those who do not have a medical background and are not familiar with the normal range of oxygen saturation and heart rate.

  • Display

    Screen color and size can make a difference in reading the displayed data. Pick a display that you can read with no trouble.

  • Durability and Battery Life

    If you only need it for personal use, you don't have to get anything particularly rugged. To measure oxygen intermittently, long battery life is not necessary. Continuous oxygen saturation measurements need either a long-lasting battery or a plug-in device.

  • Size of Probe

    Most probes come in the 0.3 inches (0.8 cm) to 1-inch size range, which can accommodate most adult fingers. You'll only need to seek another option if your fingers are either very large or very small.

  • Portability

    Some devices are portable and some are not. If you want the device to be with you all the time, and you need to carry it in your pocket or purse, a small-sized, easy-to-use portable oximeter must be your pick.

  • Ease of Use

    For people who are going to operate the oximeter on their own, the highest priority must be to check if the device is easy to use. Buying a device that is difficult to use will be a waste of money.

We hope you now have a basic understanding of what a Pulse Oximeter is how it functions. Buying a pulse oximeter can be a tricky decision because of the thousands of options available in the market. Whenever you buy one, keep in mind all these features and opt for one that meets your needs.

Helpful Information

What is a pulse oximeter and what does it do?

A pulse oximeter is a non-invasive medical device that measures the saturation of oxygen in a person's red blood cells. It clips onto a body part like a finger or earlobe, and uses light wavelengths to determine the level of oxygen saturation in the blood, along with pulse rate.

How does a pulse oximeter work?

A pulse oximeter works by emitting beams of light, typically red and infrared, through the skin to the blood vessels. It measures the changes in light absorption in oxygenated or deoxygenated blood, thus calculating the oxygen saturation level.

Who should use a pulse oximeter?

Pulse oximeters are used by anyone who needs to monitor their oxygen saturation level. This includes individuals with respiratory or cardiovascular conditions, such as COPD, asthma, pneumonia or heart failure, and those receiving supplemental oxygen. However, it's always recommended to use it under the advice of a healthcare professional.

What is a normal reading on a pulse oximeter?

A normal reading on a pulse oximeter typically falls between 95% and 100% oxygen saturation. However, this can vary based on an individual's health condition. Readings below 90% are generally considered low and warrant immediate medical attention.

How accurate are pulse oximeters?

When used correctly, pulse oximeters are typically quite accurate, usually within a 2% deviation of invasive arterial blood gas analysis. However, their accuracy can be affected by factors like poor circulation, skin temperature, skin thickness, and the use of nail polish or artificial nails.

Are there any risks associated with using a pulse oximeter?

Pulse oximeters are generally safe and pose minimal risks. They are non-invasive and do not cause pain. However, some people may experience slight discomfort or pressure where the device is clipped, and prolonged use can potentially cause skin irritation.

Where can I buy a pulse oximeter?

Pulse oximeters can be purchased at most drugstores, medical supply stores, and online marketplaces like Amazon. It's important to purchase from a reputable seller and ensure that the device meets FDA or equivalent standards.

How to use a pulse oximeter correctly?

To use a pulse oximeter, simply clip it onto a finger, making sure it's warm and relaxed. Remove any nail polish or artificial nails, as they can affect the accuracy. Wait until the reading stabilizes (usually a few seconds) before noting the result. Always follow the manufacturer's instructions for use.

Can I use a pulse oximeter to monitor for COVID-19 at home?

A pulse oximeter can be used to monitor oxygen levels at home if you're diagnosed with COVID-19, as one of the signs of severe illness is a drop in oxygen saturation. However, it should not be the sole basis for making decisions about seeking medical care and should be used under the guidance of a healthcare professional.

Why is my pulse oximeter giving me different readings on different fingers?

Different fingers can give different readings due to differences in blood circulation, skin thickness, and temperature. For consistent results, it's generally recommended to use the same finger each time.

What is the difference between a pulse oximeter and a blood gas analysis?

A pulse oximeter provides a quick, non-invasive estimate of oxygen saturation in the blood. A blood gas analysis, on the other hand, is an invasive procedure that measures the levels of oxygen and carbon dioxide directly from an arterial blood sample, providing more precise and detailed information.

Can smoking affect pulse oximeter readings?

Yes, smoking can affect pulse oximeter readings. Carbon monoxide, a gas present in cigarette smoke, binds to hemoglobin in the blood more readily than oxygen does. This can lead to falsely high pulse oximetry readings, despite the body being starved of oxygen.

How do pulse oximeters measure heart rate?

Pulse oximeters measure heart rate by detecting the pulsatile flow of blood, which corresponds to the heartbeat. Each pulse corresponds to a heartbeat, thus providing the heart rate reading.

Why is a pulse oximeter useful in diagnosing sleep apnea?

A pulse oximeter can help in diagnosing sleep apnea by revealing drops in oxygen saturation during sleep, which can occur when breathing stops or becomes shallow due to sleep apnea. However, it should be used as part of a comprehensive sleep study under professional supervision.

Can I use a pulse oximeter on a toddler or infant?

Yes, there are specially designed pediatric pulse oximeters for use on small fingers. However, they should only be used under the guidance of a healthcare professional, as children's oxygen saturation levels can vary from adults.

Can cold hands affect pulse oximeter readings?

Yes, cold hands can affect pulse oximeter readings. Cold hands often have poor blood flow, and the oximeter relies on a good flow of blood to the finger to obtain accurate readings. Warming up the hands can usually resolve this issue.

What is the importance of continuous monitoring with a pulse oximeter?

Continuous monitoring with a pulse oximeter can provide real-time insights into a person's oxygen saturation and pulse rate, which is crucial in managing various health conditions like COPD, heart disease or during a severe illness such as COVID-19. It helps in identifying any sudden changes that may require medical intervention.

Can pulse oximeters detect heart arrhythmias?

While pulse oximeters can measure pulse rate, they are not designed to detect heart arrhythmias or irregular heartbeats. They may show unusual pulse patterns in the presence of an arrhythmia, but a medical-grade heart monitor or electrocardiogram (ECG) is required for accurate diagnosis.

How can I ensure the accuracy of my pulse oximeter readings?

To ensure the accuracy of pulse oximeter readings, make sure the finger is warm, relaxed and not artificially colored with nail polish. Rest your hand at chest level and wait for the reading to stabilize. Always use the device as per the manufacturer's instructions. If the readings are consistently low or show sudden drops, seek medical attention.


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